purpose of the creed of Islam

Islamic theology has a lot of good goals that must be adhered to, namely:

law's birthday celebrated

What is the law of celebrating the passage of one or two years or more, or less than two years from the birth of a person who called or blowing out birthday candles. And what is legal to attend this feast. Is when a person shall be invited to attend the event or not. Give us an answer. And may God reward you.